This is good news for Star Trek
, certainly - there's no evidence that anyone other than he and the people he has working with him can make the Franchise work at this point. If Trek fans are lucky, the studio will keep him on as producer to guide the new director and other creatives after he's made the third one.
As for SW, I suspect the real reason JJ (and all those other directors) don't want to do it is because SW just doesn't seem all that cool to them anymore. The dull and overblown prequels killed their enthusiasm for this world just like it did for many of us.
Possibly. Star Wars
fans would be lucky beyond their reasonable expectations to have Abrams doing those movies.